INTERFEROMETRIC BACK FOCAL-PLANE MICROELLIPSOMETRY

We present a technique for ellipsometric analysis of materials with hi gh lateral resolution. A Michelson-type phase-shifting interferometer measures the phase distribution in the back focal plane of a high nume rical aperture objective. Local measurements of the ellipsometric para meter delta are performed over the entire spectrum of angles of incide nce. We show that delta is to leading order linearly proportional to t he phase change on reflection of normally incident light. We furthermo re invert the Fresnel reflection equations and derive expressions for the real and imaginary parts of the refractive index as functions of t he phase change on reflection and the reflectivity at normal incidence , both of which are measurable with the same apparatus. Hence we accom plish local measurements of the refractive indices of our samples. Det ermination of the phase change on reflection permits correction of int erferometric topography measurements of heterogeneous specimens. (C) 1 998 Optical Society of America.